grizzly: ServiceGroup monitoring APIs

[Tom Fifield]

If https://review.openstack.org/#/c/10903/ is merged, it adds new APIs for ServiceGroup Monitoring.

    Summary:
    * provide a pluggable ServiceGroup monitoring API
    * refactor the old DB-based implementation to the new API

    Currently nova compute nodes periodically write to the database (every
    10 seconds by default) to report their liveness. This implementation
    factors out this functionality and make it a set of abstract internal
    APIs with a pluggable backend implementation. Currently it's named as
    ServiceGroup APIs.

    With this effort, we are hopeful to see the following benefits:

     * We expect to see more backend implementations in addition to the
    default database-based one, such as ZooKeeper (as described in
    blueprint zk-service-heartbeat) or rabbitmq heartbeat based.

     * We expect the code to live in openstack-common so projects other
    than Nova can take advantage of the internal APIs.

     * Lay the foundations to use lower overhead heartbeat mechanisms
    which scale better.

     * Other than reporting whether a node in a service group is up or
    down, the code may also be used to query for members. Other parts of
    the code could also take advantage of the new APIs. One noteable
    example is the MatchMaker in the rpc library, which may even become
    redundant. We have been working with Eric at Cloudscaling to see how
    this fits with the matchmaker. It is likely that this code will need
    to be used, at least by the peer-to-peer based RPC mechanisms, to
    implement the new create_worker method.

    DocImpact: new config options

[Tom Fifield (fifieldt)]

Patch is merged

[Tom Fifield (fifieldt)]

cfg.StrOpt('servicegroup_driver',
   32 default=_default_driver,
   33 help='The driver for servicegroup service.')

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/21044

[Tom Fifield (fifieldt)]

Related patch - zookeeper support: https://bugs.launchpad.net/openstack-manuals/+bug/1106449

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/21044
Committed: http://github.com/openstack/openstack-manuals/commit/882f733856d949448a6e4d1d445b478b2a425abb
Submitter: Jenkins
Branch: master

commit 882f733856d949448a6e4d1d445b478b2a425abb
Author: Tom Fifield <email address hidden>
Date: Sat Feb 2 19:54:33 2013 +1100

    Add servicegroup_driver config option

    fixes bug 1084500

    Grizzly introduced the ServiceGroup APIs in nova - a set of abstract
    internal APIs with pluggable backend to deal with the reporting of
    'aliveness' by nova- services

    Change-Id: I2a0d14da08a0d9143bb15db4b292b8ef2db688fb